Camera-assisted method separates mirror defects from test alignment errors

Researchers at the Chinese Academy of Sciences demonstrated a method that separates fixed offsets inside a large mirror from temporary alignment errors in its test equipment. Applied to a four-meter-class monolithic mirror, it produced a combined standard uncertainty of 31 micrometers, according to a study in Measurement. Four industrial cameras measured movement in the test path. Researchers used those measurements to remove its contribution from optical interference data, isolating the offset between reflecting surfaces. They also demonstrated feedback during polishing, when corrections remain possible. The method measures lateral displacement in a two-dimensional plane, rather than every component of relative position and orientation.